Is the Tokina 11-16mm f/2.8 AT-X Pro DX Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 13mm f/2.8 test image. Observe the contrast and resolution of these results.
Is the Tokina 11-16mm f/2.8 AT-X Pro DX Lens set to 13mm f/2.8 sharper than the Nikon 10-24mm f/3.5-4.5G AF-S DX Nikkor Lens set to 18mm f/11.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.